"""
【黑盒，无参内构】
外观模式(Facade Pattern): 提供一个简单的接口，用于访问底层复杂系统的一些功能（相当于向上屏蔽）
"""


class SubsystemA:
    def operation_a(self):
        pass


class SubsystemB:
    def operation_b(self):
        pass


class Facade:
    def __init__(self):
        self._subsystem_a = SubsystemA()
        self._subsystem_b = SubsystemB()

    def operation(self):
        self._subsystem_a.operation_a()
        self._subsystem_b.operation_b()


facade = Facade()
facade.operation()
